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D9.A.4.1 Design for Flexure

Reinforcement for positive and negative moments are calculated on the basis of section properties provided by the user. Program first try to design the section for g = 0 and pt = balanced reinforcement ratio. If allowable moment is lower than the actual moment program increases g value for same pt and checks the satisfactory conditions. If conditions are not satisfied this procedure continues until g reaches to 1.0 and then pt value is increased keeping g = 1.0. This procedure continues until pt reaches to its maximum value( 2 % ). But if the allowable moment for pt = maximum value and g = 1.0 is lower than the actual moment the program gives message that the section fails.

This program automatically calculates the Bar size and no. of bars needed to design the section. It arranges the bar in layers as per the requirements and recalculate the effective depth and redesign the sections for this effective depth.


  1. Beams are designed for MZ only. The moment MY is not considered in flexure design

  2. MMAG parameter can be used to increase design moment

  3. 1.4 cm. is added to the clear cover to take stirrup size into consideration for flexure design.

  4. STAAD beam design procedure is based on the local practice and considering the fact that Japan is a high seismic zone area.